Fmrp Interacts with Adar and Regulates RNA Editing, Synaptic Density and Locomotor Activity in Zebrafish.

Abstract

Fragile X syndrome (FXS) is the most frequent inherited form of mental retardation. The cause for this X-linked disorder is the silencing of the fragile X mental retardation 1 (fmr1) gene and the absence of the fragile X mental retardation protein (Fmrp). The RNA-binding protein Fmrp represses protein translation, particularly in synapses. In Drosophila, Fmrp interacts with the adenosine deaminase acting on RNA (Adar) enzymes. Adar enzymes convert adenosine to inosine (A-to-I) and modify the sequence of RNA transcripts. Utilizing the fmr1 zebrafish mutant (fmr1-/-), we studied Fmrp-dependent neuronal circuit formation, behavior, and Adar-mediated RNA editing. By combining behavior analyses and live imaging of single axons and synapses, we showed hyperlocomotor activity, as well as increased axonal branching and synaptic density, in fmr1-/- larvae. We identified thousands of clustered RNA editing sites in the zebrafish transcriptome and showed that Fmrp biochemically interacts with the Adar2a protein. The expression levels of the adar genes and Adar2 protein increased in fmr1-/- zebrafish. Microfluidic-based multiplex PCR coupled with deep sequencing showed a mild increase in A-to-I RNA editing levels in evolutionarily conserved neuronal and synaptic Adar-targets in fmr1-/- larvae. These findings suggest that loss of Fmrp results in increased Adar-mediated RNA editing activity on target-specific RNAs, which, in turn, might alter neuronal circuit formation and behavior in FXS.

• Authors: Adi Shamay-Ramot, Khen Khermesh, Hagit T Porath, Michal Barak, Yishay Pinto, Chaim Wachtel, Alona Zilberberg, Tali Lerer-Goldshtein, Sol Efroni, Erez Y Levanon, Lior Appelbaum
• Journal: PLoS genetics (PLoS Genet) Vol. 11 Issue 12 Pg. e1005702 (Dec 2015) ISSN: 1553-7404 [Electronic] United States
• PMID: 26637167 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)

Chemical References

• FMR1 protein, human
• Fmr1 protein, zebrafish
• RNA-Binding Proteins
• Zebrafish Proteins
• Fragile X Mental Retardation Protein
• ADARB1 protein, human
• Adenosine Deaminase

Topics

• Adenosine Deaminase (biosynthesis, genetics)
• Animals
• Axons (metabolism, pathology)
• Disease Models, Animal
• Fragile X Mental Retardation Protein (biosynthesis, genetics)
• Fragile X Syndrome (genetics, pathology)
• Gene Expression Regulation, Developmental
• Humans
• Motor Activity (genetics)
• Neurons (metabolism, pathology)
• RNA Editing (genetics)
• RNA-Binding Proteins (biosynthesis, genetics)
• Synapses (metabolism, pathology)
• Transcriptome (genetics)
• Zebrafish
• Zebrafish Proteins (biosynthesis, genetics)